This invention relates to methods of securing gear members onto shaft members for use in installations such as gear pumps and similar applications which involve extreme loads. More particularly, the invention relates to methods of axial retention of gears on shafts in situations in which vibration, and shock loading is unusually severe in the axial dimension of the gear-shift system.
As is well appreciated by those skilled in this art, any cutting or removal of metal in either gear or shaft member will increase the likelihood of fatigue failure of the respective member. For this reason, a common method of joining the gear and shaft members involves making the internal diameter of the gear slightly smaller than the outside shaft diameter, and heating the gear to several hundred degrees Fahrenheit. Simultaneously, the shaft is cooled and then placed within in the bore of the gear. As the temperatures begin to equalize, the swelling of the shaft and shrinking of the gear will result in the joining of the members wherein the shaft and gear are under compression in the contact zone between them.
This particular means has been satisfactory in terms of ensuring the radial securement of the gear to the shaft, that is, in the routine torsional loading environments tending to force the gear member to rotate relative to the shaft member. However, in gear pump and other environments subjected to axial loading, axial forces on the gears will tend to shift the gears axially relative to the shafts, thus causing the shafts to move longitudinally out of the gears.
Notwithstanding the increased likelihood of fatigue failure, conventional means of axial securement of gears on shafts to withstand the latter type of extreme loading have involved keys, pins, snap rings, and other axial holding mechanisms which require cutting of the shaft or gear or both. The result has been short fatigue life expectancies of gear-shaft systems employed in such axial load environments.